JustificationThis recently-split species is listed as Endangered as it has an extremely small population which is threatened by habitat loss, with potential causes including invasive species, storms and wood-cutting.

Taxonomic noteNesospiza acunhae (Sibley and Monroe 1990, 1993) has been split into N. acunhae (Inaccessible Island) and N. questi (Nightingale Island), while subspecies N. wilkinsi dunnei (Inaccessible Island) has been transferred to N. acunhae following Ryan et al. (2007) and Ryan (2008) who provide compelling phylogenetic evidence for this arrangement and point out the morphological and vocal differences supporting the treatment of paraphyletic forms questi and acunhae as species.

Distribution and populationNesospiza wilkinsi is restricted to Nightingale Island, Tristan da Cunha (St Helena to UK), in the South Atlantic Ocean (Ryan 2008). It rare on the island and may number between 50 and 100 pairs (Ryan 1992, P. G. Ryan in litt. 1999, 2010), with other estimates suggesting fewer than 120 birds (Ryan 2008). The total population has probably always been small (Fraser and Briggs 1992), but may have increased slightly since the 1950s.

Population justificationThe population is currently thought to be around 100 pairs (P. G. Ryan in litt. 2009), hence a population band of 50-249 mature individuals seems appropriate.

Trend justificationThe species's population is suspected to be stable owing to the absence of any serious and immediate threats.

EcologyIt is largely restricted to areas which support some Phylica arborea trees, but also regularly occurs in tussock-grassland. The breeding season is from December to February, with nests located in clumps of vegetation near ground-level.

Threats

Visits to Nightingale can now be made by islanders via at least two RIBs as well as the fishery patrol vessel and the crayfish vessel operating in Tristan waters (P. G. Ryan in litt. 2012). This species is thus permanently at risk from the accidental introduction of mammalian predators which could prey on eggs, chicks and nesting birds. Another threat is the invasion of the introduced New Zealand flax Phormium tenax into areas of Phylica, but initial clearing in 2004 and ongoing follow-up operations have largely eliminated this threat (P. G. Ryan in litt. 2012). It may be benefiting from the cessation of wood cutting by Tristan islanders visiting Nightingale, resulting in some Phylica regeneration, but there are reports that an alien scale insect (common on Tristan and locally common on Inaccessible) is also on Nightingale, which may have significant impacts on fruit production (P. G. Ryan in litt. 2012). On Inaccessible, heavily infested trees have much lower fruit loads than healthy trees. Another potential threat is a black fungus-like growth which has previously from Tristan to Inaccessible, though there is currently no evidence of its presence on Nightingale. It is also potentially threatened by catastrophic weather events and the effects of climate change: strong winds blow down large swathes of Phylica (as happened in 2001), potentially affecting the habitat quite significantly (P. G. Ryan in litt. 2012).

Conservation Actions UnderwayNo specific conservation actions are currently known for the species. Conservation Actions ProposedConduct surveys to obtain an up-to-date population estimate. Carry out regular surveys to monitor population trends. Minimise the risk of introduction of exotic animal or plant taxa, including soil pathogens that could affect important plant species, by strict controls on visits, and promoting awareness of the dangers of inter-island transfers (P. G. Ryan in litt. 1999, 2010). Eradicate New Zealand flax from Nightingale (P. G. Ryan in litt. 1999, 2010).

ReferencesFraser, M. W.; Briggs, D. J. 1992. New information on the Nesospiza buntings at Inaccessible Island, Tristan da Cunha, and notes on their conservation. Bulletin of the British Ornithologists' Club 112: 191-205.

Recommended citation
BirdLife International (2015) Species factsheet: Nesospiza wilkinsi. Downloaded from
http://www.birdlife.org on 03/03/2015.
Recommended citation for factsheets for more than one species: BirdLife International (2015) IUCN Red List for birds. Downloaded from
http://www.birdlife.org on 03/03/2015.

This information is based upon, and updates, the information published in BirdLife International (2000)
Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004)
Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife